Our objective is to learn more about the metabolism and mechanism of action of arsenate. Although the study will deal mainly with corn seedlings and tomato plants, much of the information obtained should be applicable to animals. This study, aimed principally at the ability of arsenate to substitute for phosphate, will explore several aspects of the biochemistry of arsenate. 1. The metabolism of 74As-arsenate in plants. Is 74As-arsenate reduced to arsenite, bound to acid-insoluble macromolecules or bound to lipids? Does arsenate or a derivative accumulate in one of these fractions or in some particular organ of a plant? What is the nature of the insoluble material bound to the 74As and the linkage with 74As? 2. The effects of arsenate on nucleic acids. Is it incorporated into DNA or RNA, does it affect DNA or RNA synthesis. Is it mutagenic and does it affect somatic crossing over? 3. The ability of plants to accumulate arsenate from the environment. Is its uptake by roots active and does it proceed via the pathway for phosphate uptake? This research has public health implications: Do plants accumulate arsenate from the environment? How? Can arsenate effect the hereditary material at low doses? In addition, it would be valuable to learn more about how it affects development at higher (herbicidal or insecticidal) levels.